You should just shorten your photoperiod instead of eliminating a day. Reducing it by an hour a day is 7 hrs over a week's time, almost an entire day's photoperiod.
hi.
In my office tank, I only use the MHs 5 days a week. During the weekend, the HVAC is off, and it is very hot in the office. However, I do leave the PC on during the weekend. I do have a chiller, but it does not work well if the air temperature is 110F.
When I hang out in Belize and Honduras you knot it does rain and storm once or more / week. I am sure the coral and other critters are used to a few dark days.. Just leave the VHO's on and kill the MH for a day
I don't think it would cause any problems unless your system is already under lighted for the critters you have.